Wine is typically made by crushing and de-stemming grapes and then extracting color and flavor components from the grape skins and pulp by allowing the crushed grapes, including their juice, to sit for a period of time referred to as an extraction period. This extraction period is followed by or is part of a fermentation stage where yeast introduced to the mixture converts the sugars in the grape juice to alcohol and carbon dioxide. The fermentation can also facilitate in extracting flavor and color from the skins. This process is often referred to as “maceration.” The liquid or partially fermented grape juice, referred to as “must”, is typically pressed from the skins, stems, and other solids, collectively referred to as “pomace,” and transferred to a secondary vessel for further processing.
During the extraction period the large solids typically float to the surface of the crushed grapes to form a “cap.” This cap can be relatively thick and portions can partially dry out, which diminishes extraction. If fermentation is occurring, the carbon dioxide formed by the yeast can also carry solids to the surface because the gas bubbles nucleate on the solids and carry them to the top of the liquid.
In order to improve the extraction of flavor and color, the cap can kept moist by a number of techniques including manual methods used by the winemaker to push portions of the cap into the must. The resulting combination of must and pomace is a non-homogenous mixture of liquids and solids that must be separated by press operation on completion of the fermentation period.
Press operations of grapes and other vegetable substances have been traditionally carried out using vertical presses of a screw or hydraulic type, or horizontal presses of that perform compression by means of an inflatable diaphragm or compression by means of opposing circular platens, the displacement being provided by cylinders or screws.
A vertical press typically includes a perforated basket, drum or like container having slots, holes or like flow openings in its longitudinal walls, and further includes a mechanical or hydraulic-powered press mechanism that applies pressure to the mixture within the basket, thus forcing the liquid out of the basket openings. The liquid is collected in a press pan that is located immediately beneath the basket, the pan having a spout or valve that allows the liquid to be retained within the press pan and, when desired, to then be transferred for further processing or to a storage container.
The press operation is typically conducted in batches limited to the size of the basket. Each batch must be separately loaded into the basket and placed under the press mechanism, or loaded into a basket already located under the press. A problem encountered with this process is that the must will begin to flow freely under its own weight from the basket openings as soon as the must and pomace mixture is introduced to the basket, resulting in waste. Furthermore, should the extracted liquid volume exceed the capacity of the press pan, additional waste results when the press pan overflows.
The risk of overflow and loss of valuable product is increased with the additional delays of positioning the basket beneath the press, or by attempting to load an already positioned basket while working around the interference created by the press mechanism. Filling a basket prior to placement under the press can also result in loss of product as the liquid in the rapidly filling press pan splashes over the edges during transport. Further processing delays can occur as the basket is removed for disposal of the resulting compressed solid material.
A second problem arises in the press operation in that uneven pressures are produced within the mass of non-homogenous must and pomace as pressure is applied by the press mechanism. Pockets of liquid become trapped within the compressing mass, which increasingly acts as a solid that is impervious to the liquid trapped within. As pressure from the press is increased, the liquid in these pockets can eventually be forcefully ejected laterally, often times creating further waste of product, creating problems of workplace cleanliness, and raising the possibility of injury.
Another problem with the press operation is the existence of sludge that naturally forms as heavier particulate matter settles within the must and pomace mixture, particularly in the lower portion of the basket and press pan prior to pressing. Sludge is troublesome in that it can contaminate the outflowing liquid and otherwise foul filters and pumps, resulting in waste, production inefficiencies, and undesirable wine characteristics.
A wine maker will often sample the outflowing liquid and will stop the press operation when the characteristics of the liquid become undesirable. While wine presses of the prior art are typically equipped with a press mechanism, a press basket, and a press pan to collect the extracted liquid, there remains a need for an additional reservoir that would allow the wine maker to hold an entire batch of liquid, or a substantial portion thereof, from the press before transferring it to a holding vessel. An additional reservoir would allow the wine maker the ability to chemically treat the liquid as one lot before transferring the it to a barrel, the option of blending the various flavors extracted at different phases of the press cycle before transferring the liquid to a barrel, and the ability to ascertain the quality of the entire batch of liquid before transferring the liquid for further processing or storage.
Inspection of visual quality of extracted liquid is especially important for making white wine, where it is desirable to visually ascertain and inspect the clarity and percent of suspended solids in the fluid at the time of pressing. Unlike the process for making red wines, white wine usually requires that the grapes be placed directly in a basket press “whole” to extract the liquid before fermentation begins. The basket press then does the initial liquid extraction instead of the crusher de-stemmer as for red wine. The white wine maker needs to know how much suspended solid is in the white grape juice, often by making a visual assessment of the extracted liquid and before the liquid is transferred to other containers for fermentation.
Press operations for extracting liquids from suspended solids, using either vertical or horizontal presses, results in a disk of compressed solid matter within the press basket, referred to as a “cake,” and requires removal from the basket prior to the winemaker's refilling the basket for the next extraction cycle.
Following each extraction cycle in earlier wine presses, it was necessary to perform a manual breaking-up operation using shovels and forks to dislodge and remove the cake. On pneumatic horizontal presses, the breaking-up operation is performed mechanically, by rotation of the basket, after decompression of the diaphragm. On horizontal presses with compression by means of opposing circular platens, this operation is carried out by rotation of the basket together with retraction of the platens. Although mechanization of the breaking-up operation has dispensed with laborious manual interventions, it has introduced crushing and grinding processes which
impair quality through introduction of undesirable sludge and turbidity.
U.S. Pat. No. 4,730,555 teaches a wine press with horizontally oriented rotatable platen that provides for an extraction process that, when the substance to be pressed is introduced into the basket or cage, a perforated rotating horizontal circular platen allows for uniform distribution of the substance. After closure of the basket, the two thrust platens are brought together in successive pressure stages until the desired degree of extraction is obtained. The final cake forming the residue is then removed under its own weight. While this invention provides a means of removing a resulting cake following a press operation, it does not address the issues involved for cake extraction using a vertical press and the loss of product as a basket is loaded or positioned in preparation for pressing. This invention further does not address the extraction of trapped pockets of fluid that may exist within a mass of compressing substance.
U.S. Pat. No. 5,927,187 teaches a wine or fruit press having a drum or similar container having slots, holes or similar flow openings in its longitudinal sides and a feed plat or similar component longitudinally movable inside the container. This invention provides improved press efficiency and low sludge content over prior art but does not address the need for the issues involved for cake extraction using a vertical press and the loss of product as a basket is loaded or positioned in preparation for pressing. This invention further does not address the extraction of trapped pockets of fluid that may exist within a mass of compressing substance.
Some commercially available wine presses are equipped with casters on the press frame base, and a separate frame for supporting a press basket and press pan that is also equipped with casters, for independently positioning the press and the press basket. Problems of liquid overflow and losses due to positioning of the press and press basket are not sufficiently addressed by these presses.